描述

The date utility writes the date and time to standard output or attempts
to set the system date and time. By default, the current date and
time is written.

Specifications of native language translations of month and weekday names are supported. The
month and weekday names used for a language are based on the locale
specified by the environment variable LC_TIME. See environ(5).

The following is the default form for the C locale:

%a %b %e %T %Z %Y

For example,

Fri Dec 23 10:10:42 EST 1988

选项

The following options are supported:

-a [ - ] sss.fff

Slowly adjust the time by sss.fff seconds (fff represents fractions of a second). This adjustment can be positive or negative. The system's clock is sped up or slowed down until it has drifted by the number of seconds specified. Only the super-user may adjust the time.

-u

Display (or set) the date in Greenwich Mean Time (GMT—universal time), bypassing the normal conversion to (or from) local time.

操作数

The following operands are supported:

+format

If the argument begins with +, the output of date is the result of passing format and the current time to strftime(). date uses the conversion specifications listed on the strftime(3C) manual page, with the conversion specification for %C determined by whether /usr/bin/date or /usr/xpg4/bin/date is used:

/usr/bin/date

Locale's date and time representation. This is the default output for date.

/usr/xpg4/bin/date

Century (a year divided by 100 and truncated to an integer) as a decimal number [00-99].

Additionally, date supports %N which represents nanosecond portion of the current time since Epoch (00:00:00 UTC, January 1, 1970) as a decimal number [000000000-999999999]. The conversion specification accepts an optional flag character, an optional field width, or both as specified in strftime() with a difference that, if a field width specified is less than nine, the actual date output contains only the specified amount of digits of the nanoseconds from left.

The string is always terminated with a NEWLINE. An argument containing blanks must be quoted; see the EXAMPLES section.

mm

Month number

dd

Day number in the month

HH

Hour number (24 hour system)

MM

Minute number

SS

Second number

cc

Century (a year divided by 100 and truncated to an integer) as a decimal number [00-99]. For example, cc is 19 for the year 1988 and 20 for the year 2007.

yy

Last two digits of the year number. If century (cc) is not specified, then values in the range 69–99 shall refer to years 1969 to 1999 inclusive, and values in the range 00–68 shall refer to years 2000 to 2068, inclusive.

The month, day, year number, and century may be omitted; the current values
are applied as defaults. For example, the following entry:

example% date 10080045

sets the date to Oct 8, 12:45 a.m. The current year is
the default because no year is supplied. The system operates in GMT. date
takes care of the conversion to and from local standard and daylight time.
Only the super-user may change the date. After successfully setting the date and time,
date displays the new date according to the default format. The date command
uses TZ to determine the correct time zone information; see environ(5).

示例

示例 1 Generating Output

The following command:

example% date '+DATE: %m/%d/%y%nTIME:%H:%M:%S'

generates as output

DATE: 08/01/76
TIME: 14:45:05

示例 2 Setting the Current Time

The following command sets the current time to 12:34:56:

example# date 1234.56

示例 3 Setting Another Time and Date in Greenwich Mean Time

The following command sets the date to January 1st, 12:30 am, 2000:

example# date -u 010100302000

This is displayed as:

Thu Jan 01 00:30:00 GMT 2000

环境变量

See environ(5) for descriptions of the following environment variables that affect the execution of
date: LANG, LC_ALL, LC_CTYPE, LC_TIME, LC_MESSAGES, and NLSPATH.

TZ

Determine the timezone in which the time and date are written, unless the -u option is specified. If the TZ variable is not set and the -u is not specified, the system default timezone is used.

/usr/xpg4/bin/date

另请参见

诊断

no permission

You are not the super-user and you tried to change the date.

bad conversion

The date set is syntactically incorrect.

附注

If you attempt to set the current date to one of the
dates that the standard and alternate time zones change (for example, the date
that daylight time is starting or ending), and you attempt to set the
time to a time in the interval between the end of standard time
and the beginning of the alternate time (or the end of the alternate
time and the beginning of standard time), the results are unpredictable.

Using the date command from within windowing environments to change the date can
lead to unpredictable results and is unsafe. It can also be unsafe in
the multi-user mode, that is, outside of a windowing system, if the date
is changed rapidly back and forth. The recommended method of changing the date
is 'date-a'.

Setting the system time or allowing the system time to progress beyond
03:14:07 UTC Jan 19, 2038 is not supported on Solaris.